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    <script>
        // console.dir(Set)
        let s1 = new Set([1,2,3,2,1,5,6,7])
        // console.log(s1);       //{1,2,3,,5,6,7}
        // console.log(s1.size);  // 6
        for(let item of s1){
            console.log(item)
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        s1.add(12)
        s1.add(2).add(100).add(200)
        console.log(s1);
        s1.delete(2)
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